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LINEAR QUADRATIC OPTIMAL GUIDANCE WITH ARBITRARY WEIGHTING FUNCTIONS
CHANG-HUN LEE 한국산업응용수학회 2015 Journal of the Korean Society for Industrial and A Vol.19 No.3
In this article, the linear quadratic (LQ) optimal guidance laws with arbitrary weighting functions are introduced. The optimal guidance problems in conjunction with the control effort weighed by arbitrary functions are formulated, and then the general solutions of these problems are determined. Based on these investigations, we can know a lot of previous optimal guidance laws belong to the proposed results. Additionally, the proposed results are compared with other results from the generalization standpoint. The potential importance on the proposed results is that a lot of useful new guidance laws providing their outstanding performance compared with existing works can be designed by choosing weighting functions properly. Accordingly, a new optimal guidance law is derived based on the proposed results as an illustrative example.
Nonlinear Missile Autopilot Design via Three Loop Topology and Time-Delay Adaptation Scheme
Chang-Hun Lee,Byung-Eul Jun,Jin-Ik Lee,Min-Jea Tahk 제어로봇시스템학회 2013 제어로봇시스템학회 국제학술대회 논문집 Vol.2013 No.10
In this paper, a new missile acceleration controller is proposed, based on the three loop control structure with the feedback linearization control law and time-delay adaptive law. In order to avoid the nonminimum characteristics of conventional missile systems, an approximate system and three loop topology are considered. Under this control structure, the feedback linearization methodology is applied to relieve difficulties of aerodynamic nonlinearity. Finally, this controller is augmented by the time-delay adaptation scheme to compensate for the model uncertainties. The performance of proposed autopilot is tested using a nonlinear missile model with uncertainties, by imposing step commands.
Biased PNG for target observability enhancement against nonmaneuvering targets
Chang-Hun Lee,Tae-Hun Kim,Min-Jea Tahk IEEE 2015 IEEE transactions on aerospace and electronic syst Vol.51 No.1
<P>This paper proposes a biased proportional navigation guidance (BPNG) law providing enhanced target observability for passive homing missile systems against a nonmaneuvering target. After examining the line-of-sight (LOS) rate equation, which is an important parameter of target observability and which reveals that the LOS rate is proportional to the rate of cross-range deviation, a bias term of BPNG is formulated using the rate of cross-range deviation to generate an additional LOS rate. The closed-form trajectory solution of the proposed guidance law is derived, and its capturability and characteristics are then investigated. Using numerical simulations, the performance of the proposed guidance law is determined in conjunction with a target state estimator.</P>
Chang-Hun Lee,Min-Jea Tahk 한국항공우주학회 2010 International Journal of Aeronautical and Space Sc Vol.11 No.2
This paper deals with a new method of unmanned aerial vehicle (UAV) recovery when a UAV fails to get a global positioning system (GPS) signal at an unprepared site. The proposed method is based on the simultaneous localization and mapping (SLAM) algorithm. It is a process by which a vehicle can build a map of an unknown environment and simultaneously use this map to determine its position. Extensive research on SLAM algorithms proves that the error in the map reaches a lower limit, which is a function of the error that existed when the first observation was made. For this reason, the proposed method can help an inertial navigation system to prevent its error of divergence with regard to the vehicle position. In other words, it is possible that a UAV can navigate with reasonable positional accuracy in an unknown environment without the aid of GPS. This is the main idea of the present paper. Especially, this paper focuses on path planning that maximizes the discussed ability of a SLAM algorithm. In this work, a SLAM algorithm based on extended Kalman filter is used. For simplicity’s sake, a blimp-type of UAV model is discussed and three-dimensional pointed-shape landmarks are considered. Finally, the proposed method is evaluated by a number of simulations.
Missile Autopilot Design for Agile Turn Using Time Delay Control with Nonlinear Observer
Chang-Hun Lee,Tae-Hun Kim,Min-Jea Tahk 한국항공우주학회 2011 International Journal of Aeronautical and Space Sc Vol.12 No.3
This paper deals with missile autopilot design for agile turn phase in air-to-air engagement scenarios. To attain a fast response, angle-of-attack (AOA) is adopted for an autopilot command structure. Since a high operational AOA is generally required during the agile turn phase, dealing with the aerodynamic uncertainties can be a challenge for autopilot design. As a remedy, a new controller design method based on robust nonlinear control methodology such as time delay control is proposed in this paper. Nonlinear observer is also proposed to estimate the AOA in the presence of the model uncertainties. The performance of the proposed controller with variation of the aerodynamic coefficients is investigated through numerical simulations.